Response of a single 'mega intramuscular dose' of vitamin D on serum 25OHD and parathyroid hormone levels
OBJECTIVE: To determine the changes produced in serum 25OHD and iPTH levels after 600,000 IU of injection cholecalciferol in volunteers.
STUDY DESIGN: Interventional study.
PLACE AND DURATION OF STUDY: Section of Chemical Pathology, Department of Pathology and Microbiology, the Aga Khan University Hospital, Karachi, from June 2009 - June 2010.
METHODOLOGY: Volunteers of either gender aged 18-40 years with known 25OHD, calcium (Ca), creatinine (Cr) and phosphorous (P) levels were included in the study. Subjects on therapy like vitamin D and calcium supplements, corticosteroids or anti-epileptic medicines, primary hyperparathyroidism and hypercalcaemia, with co-morbidity like renal failure, liver disease and history of malabsorption, diarrhea or hyperthyroidism were excluded. All volunteers were given an intramuscular injection of vitamin D3 (cholecalciferol, 600,000 IU). After 8 weeks, serum 25OHD, iPTH, Ca and P levels were determined again. For 25OHD level, cut-off of 50 nmol/l was defined as deficient, 50-75 nmol/l as insufficient and 75 as optimal level.
RESULTS: Mean 25OHD and iPTH levels were 35.06 16.6 nmol/l and 81.15 76.78 pg/ml respectively at baseline. Seventeen volunteers were 25OHD deficient. Five had high iPTH levels (25%) (mean 156 123.7 pg/ml). 25OHD and iPTH showed a significant inverse correlation at baseline (< 0.01). After 8 weeks of injection vitamin D 25OHD levels became optimal in 6 subjects (35%) [mean 92.9 16.6 nmol/l]. It remained low in 5 volunteers (25%) [mean 41.6 9.6 nmol/l] while insufficient levels were seen in 9 volunteers (40%) [mean 63.35.8 nmol/l]. Follow-up mean Ca, P and iPTH were 2.25 mmol/l ( 0.09), 1.1 ( 0.1) and 47.52 pg/ml ( 22.56) respectively. A significant increase in mean 25OHD level was seen at follow-up (p < 0.01), while the change in PTH was insignificant (p=0.05).
CONCLUSION: Single mega-dose of cholecalciferol achieved optimal levels of 25OHD in 35% of subjects after eight weeks of supplementation.